Speed stabilized vacuum deposited silver halide



May 6, 1969 A. A. RASCH ET AL 3,442,649

SPEED STABILIZED VACUUM DEPOSITED SILVER HALIDE Filed Dec. 5, 1964 H YDROPH/L l6 OVERCOAT CONTAIN/N6 SEA/SI T/ZER SILVER HAL IDE' A SUPPORT ARTHUR A. RASCH' JEAN E JONES W/LBUR 6. H0065? INVENTORS AQMM BY 5% mm Patented May 6, 1969 ice 3,442,649 SPEED STABILIZED VACUUM DEPOSITED SILVER HALIDE Arthur A. Rasch, Jean E. Jones, and Wilbur C. Hodges,

Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Dec. 3, 1964, Ser. No. 415,596 Int. Cl. G03c N28 US. C]. 96-67 7 Claims ABSTRACT OF THE DISCLOSURE Photographic elements utilizing a vacuum-deposited silver halide layer as the light-sensitive component are stabiliz-ed against speed changes during storage by positioning a hydrophilic layer contiguous to the silver halide layer. Such a hydrophilic layer can contain either chemical or spectral photographic sensitizers or combinations thereof.

This invention relates to photographic elements, and more particularly to photographic elements of the type having a support carrying a vacuum deposited layer of silver halide.

It has been known for a number of years that light sensitive elements may be provided which comprise a support carrying a vacuum deposited layer of silver halide. De Boer et al. in US. Patent 1,970,496 described a method for the preparation of such elements in 1934 which involved coating a support with a light sensitive metal salt, e.g., a silver halide, by sublimation. Such elements have never been commercially successful, principally because of the very slow photographic speed thereof. It is, therefore, highly desirable to provide some manner of substantially increasing the speed of these elements, and broadening the response thereof to a wider region of the visible spectrum.

A further disadvantage of the prior art photographic elements having a vacuum deposited silver halide layer is that upon storage, the speed of the element first increases considerably, up to about four times its original value, and then drops to approximately one-half or less of the original value. It is, of course, highly desirable that photographic elements have a predictable stable speed to permit correct exposure.

This invention provides a method for chemically and spectrally sensitizing photographic elements of the type having a vacuum deposited light sensitive silver halide layer, and means for stabilizing the speed of such elements during storage.

One object of our invention is to provide photographic elements of the type having a vacuum deposited light sensitive silver halide layer, which elements are stabilized against speed changes.

Another object of our invention is to provide chemically sensitized photographic elements of the type having a vacuum deposited light sensitive silver halide layer.

A further object of our invention is to provide spectrally sensitized photographic elements having a vacuum deposited light sensitive silver halide layer.

Still another object of our invention is to provide a process for sensitizing and stabilizing photographic elements having a vacuum deposited light sensitive silver halide layer.

Other objects of our invention will appear herein.

In one embodiment of our invention, we provide photographic elements of the type having a support carrying a vacuum deposited light sensitive silver halide layer with a hydrophilic overcoating. We have found that the hydrophilic overcoating unexpectedly functions to stabilize vacuum deposited silver halide layers against changes in speed on storage.

In another embodiment of our invention, photographic elements of the type having a support carrying a vacuum deposited light sensitive silver halide layer, are sensitized by providing a hydrophilic overcoating containing spectral and/or chemical sensitizers. Although in the preferred embodiment of the invention the sensitizers are incorporated in a hydrophilic overcoating, it is also possible to provide photographic elements in which the vacuum deposited silver halide layer is over a hydrophilic coating containing spectral and/or chemical sensitizers. In the latter arrangement, a support may be coated with a hydrophilic layer containing a sensitizer, and then have vacuum deposited thereon a light sensitive layer of silver halide. Thus, the invention is broadly applicable to providing light sensitive vacuum deposited silver halide layers with a contiguous hydrophilic layer containing chemical and/or spectral sensitizers.

In another embodiment of our invention, photographic elements of the type having a support carrying a light sensitive, vacuum deposited silver halide layer, are sensitized in any convenient method, preferably by bathing the element in a solution containing a photographic sensitizer (i.e., a chemical sensitizer, a spectral sensitizer or a combination thereof) and then providing a hydrophilic coating over the sensitized silver halide layer.

Preferably, the vacuum deposited silver halide layers with which this invention is concerned are substantially free from any binder.

Our invention is further illustrated in the accompanying drawing which shows a suitable support having vacuum deposited thereon a light sensitive silver halide layer, and a hydrophilic overcoating containing sensitizer.

The invention will be further illustrated in the following examples. In these examples, the photographic elements were prepared by vacuum depositing a light sensitive layer of silver halide on a support.

Example 1 shows the sensitizing effect of a hydrophilic overcoating in accordance with the invention.

Example 1 Light sensitive photographic elements having as the light sensitive layer a deposit of silver halide were prepared by vacuum deposition using a Model LC-18B vacuum coater of the Consolidated Vacuum Corp. The materials to be evaporated were placed in boats or troughs made of thin metal strips through which an electric current was passed heating the boats and their contents. The substrates upon which the vaporized materials were condensed were placed in a dome-shaped holder some distance above the vapor source. A remotely operated shutter was placed between the vapor source and the substrate. When a coating was to be made, the boat was heated until the material began to vaporize, the shutter opened and the vapor allowed to condense until the substrate had coated thereon a film of the desired thickness. The shutter was then closed and the boat and material allowed to cool. The thickness of the coating may be determined in any convenient manner, such as by providing a glass monitor slide between the samples of substrates and in the same plane. An optical system may be employed to focus the image of the filament of an incandescent lamp on the slide and determining the intensity of the reflected light from the slide using, for example, a photocell and amplifier. As the silver halide condenses on the glass slide the thickness of the film may be measured interferometn'cally. Using this apparatus, two 5 x 10-inch sheets of polyethylene terephthalate film supports, having a conventional photographic subbing coating thereon, were placed on the substrate holder and 0.75 gram of silver bromide pellets were placed in a boat made from a strip of pure silver. The vacuum chamber was pumped down to 5 x torr and a current of 390 amperes passed through the filament. When the silver bromide was fully melted, the shutter was opened and a film 207 m was deposited on the substrate corresponding to a silver coverage of 60 mg./ sq. ft. The shutter was closed, the boat allowed to cool and the vacuum chamber returned to atmospheric pressure. Upon storage, the light sensitive film thus obtained at first increased in speed up to 4 times its original value, and then dropped to less than /2 the original speed. However, when a photographic element was prepared in the same manner, but overcoated with a thin coating of gelatin, it was found that the speed of the photographic element did not change during storage.

In addition to gelatin, a large number of hydrophilic coatings may be applied over vacuum deposited light sensitive silver halide layers to stabilize the speed thereof. Preferably, the overcoating is permeable to photographic developers. Among the useful hydrophilic colloids are colloidal albumen, cellulose derivatives and synthetic resins, for instance, polyvinyl compounds. Typical useful colloids which may be used are polyvinyl alcohol or a hydrolyzed polyvinyl acetate as described in Lowe U.S. Patent2,286,215 issued June 16, 1942; a far hydrolyzed cellulose ester such as cellulose acetate hydrolyzed to an acetyl content of 1926% as described in US. Patent 2,327,808 of Lowe and Clark, issued Aug. 24, 1943; a water-soluble ethanolamine cellulose acetate as described in Yutzy US. Patent 2,322,085, issued June 15, 1943; a polyacrylamide having a combined acrylamide content of 30-60% and a specific viscosity of 025- or an imidized polyacrylamide of like acrylamide content and viscosity as described in Lowe, Minsk and Kenyon US. Patent 2,541,- 474, issued Feb. 13, 1951; zein as described in Lowe US. Patent 2,563,791, issued Aug. 7, 1951; a vinyl alcohol polymer containing urethane carboxylic acid groups of the type described in Unruh and Smith US. Patent 2,768,- 154, issued Oct. 23, 1956; or containing cyano-acetyl groups such as the vinyl alcohol-vinyl cyanoacetate copolymer as described in Unruh, Smith and Priest US. Patent 2,808,331, issued Oct. 1, 1957; or a polymeric material which results from polymerizing a protein or a saturated acylated protein with a monomer having a vinyl group as described in US. Patent 2,852,382, of Illingsworth, Dann and Gates, issued Sept. 16, 1958.

The sensitization of photographic elements having a vacuum deposited silver halide layer is demonstrated in Examples 2-4.

Example 2 A photographic element was prepared as described in Example 1, and then overcoated with a 2% aqueous gelatin solution containing 0.010 gram of formaldehyde (hardener) per gram of gel. A second photographic element was prepared in exactly the same way except that 20 mg. per ml. each of sodium aurous dithiosulfate and ammonium chloroiridite were added to the gelatin solution used for overcoating. Each coating was exposed sensitometrically and developed for 20 seconds at 23 C. in the following developer:

Grams N-methyl-p-amino phenol 3.1 Sodium sulfite, des. 45.0 Hydroquinone 12.0 Sodium carbonate, des 67.5 Potassium bromide 1.9 S-mercapto-l-phenyl-l,2,3,4-tetrazole 0.1 Hypo 4.0

Water to make 1 liter.

The coatings were then fixed for 5 seconds in Kodak Rapid Liquid Fixer, rinsed briefly in water and dried. It was found that the film overcoated with gelatin containing the sensitizers was three times more sensitive than the control.

4 Example 3 Using the procedure described in Example 1, a layer of silver bromide 137 m thick was deposited on a paper substrate which had previously been overcoated with a polyvinyl alcohol-titanium dioxide emulsion, giving a silver coverage of 40 mg./ sq. ft. When the material was removed from the evaporator it was coated with a 2% solution of inert gelatin at 45 C., the solution also containing 0.1 gram per liter of the sensitizing dye anhydro-9- methyl-3,3 '-di- (3-sulfobutyl) thiacarbocyanine hydroxide. The coating was dried at room atmospheric conditions. A control element was prepared in exactly the same manner except that the sensitizing dye was omitted. The coatings were sensitometrically exposed and developed as described in Example 2. The coating containing sensitizing dye was found to have eight times the photographic speed of the control, and it was sensitive to radiation in the visible region of the spectrum up to a wavelength of 650 mp, while the control coating had sensitivity to wavelengths only up to 450 my. or less.

Example 4 Employing the procedure described in Example 1, a silver bromide layer m thick was deposited on a paper substrate to give a silver coverage of 40 mg./ sq. ft. Upon removal from the evaporator, the material was overcoated at 45 C. with a 2% solution of inert gelatin which contained the sensitizing dye 3-carboxymethyl-5-[ (3-ethyl- 2-benzothiazolinylidene)ethylidene] rhodanine. A control was prepared in exactly the same manner except that the sensitizing dye was omitted. Each coating was sensitometrically exposed and developed as described in Example 2. The coating containing the sensitizing dye was found to have 10 times the photographic speed of the control, and was sensitive to wavelengths in the visible region of the spectrum up to 650 Ill 1., while the control coating was sensitive to wavelengths of 450 m or less.

Example 5 The procedure of Example 2 was followed except that instead of incorporating the sensitizers in the gelatin overcoat, the silver halide layer was sensitized by bathing for 30 seconds at 72 F. in an aqueous solution containing 20 mg. per liter each of sodium aurous dithiosulfate and ammonium chloroiridite, prior to overcoating with gelatin. A similar increase in speed was attained.

Example 6 The procedure of Example 3 was followed except that instead of incorporating the sensitizer in the gelatin overcoat, the silver halide layer was sensitized by bathing for 30 seconds at 72 F. in a 0.01% solution of the sensitizing dye anhydro-9-methyl-3,3 '-di- 3-sulfobutyl thiacarbocyanine hydroxide, prior to overcoating with gelatin. A similar increase in spectral sensitivity was obtained.

Photographic elements of the type having a vacuum deposited silver halide layer may be sensitized by bathing the element, or by incorporating in a contiguous hydrophilic coating, a large number of photographic sensitizers (both chemical and spectral). Typical useful sensitizers include salts of the noble metals such as ruthenium, rhodium, palladium, iridium, and platinum. Representative compounds are ammonium chloropalladate, potassium chloroplatinate, and sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli US. Patent 2,448,060, issued Aug. 31, 1948, and as antifoggants in higher amounts, as described in Trivelli and Smith US. Patents 2,566,245, issued Aug. 28, 1951, and 2,566,263, issued Aug. 28, 1951.

Other useful sensitizers include gold salts as described in Waller et al. US. Patent 2,399,083, issued Apr. 23, 1946, or stabilized with gold salts as described in Damschroder US. Patent 2,597,856, issued May 27, 1952, and Yutzy and Leermakers US. Patent 2,597,915, issued May 27, 1952. Suitable compounds are potassium chloroaurite,

potassium aurithiocyanate, potassium chloroaurate, auric trichloride and 2-aurosulfobenzothiazole methochloride.

Still other useful chemical sensitizers are reducing agents such as stannous salts (Carroll U.S. Patent 2,487,850, issued Nov. 15, 1949), polyamines, such as diethyl triamine (Lowe and Jones U.S. Patent 2,518,698, issued Aug. 15, 1950), polyamines, such as spermine (Lowe and Allen U.S. Patent 2,521,925, issued Sept. 12, 1950), or bis('beta-aminoethyl)sulfide and its water-soluble salts (Lowe and Jones U.S. Patent 2,521,926, issued Sept. 12, 1950).

Highly useful optical sensitizers include cyanine and merocyanine dyes, such as those described in Brooker U.S. Patents 1,846,301, issued Feb. 23, 1932, 1,846,302, issued Feb. 23, 1932; and 1,942,854, issued Jan. 9, 1924; White U.S. Patent 1,990,507, issued Feb.. 12, 1935; Brooker and White U.S. Patents 2,112,140, issued Mar. 22, 1938; 2,165,338, issued July 11, 1939; 2,493,747, issued Jan. 10,1950, and 2,739,964, issued Mar. 27, 1956; Brooker and Keyes U.S. Patent 2,493,748, ..issued Jan. 10, 1950; Sprague U.S. Patents 2,503,776, issued Apr. 11, 1950, and 2,519,001, issued Aug. 15, 1950; Heseltine and Brooker U.S."Patent 2,666,761, issued Jan. 19, 1954; Heseltine U.S. Patent 2,734,900, issued Feb. 14, 1956; Van Lare U.S. Patent 2,739,149, issued Mar. 20, 195 6; and Kodak Limited British Patent 450,958, issued July 15, 1936.

Particularly useful spectral sensitizing dyes include those having an acidic substituent (i.e., carboxyl or sulfo, including water-soluble salts thereof, such as the sodium potassium, ammonium, etc. salts). Such dyes are described in U.S. Patents 2,503,776; 2,493,747, etc. mentioned above. They can be used in the form of their free acids, salts or anhydronium bases or hydroxides (see JACS, vol. 62, p. 1116 and U.S. 3,128,179 for examples of such dyes). Also useful are merocyanine dyes containing a basic substituent, e.g., piperidino, morpholino or aminoalkyl such as those described in Taber and Brooker U.S. patent applications S.N. 364,451; 364,780; and 364,808, all filed May 4, 1964.

Useful speed increasing compounds which may be incorporated in a hydrophilic overcoating include the quaternary ammonium type of Carroll U.S. Patent 2,271,623, issued Feb. 3, 1942; Carroll and Allen U.S. Patent 2,288,226, issued June 30, 1942; and Carroll and Spence U.S. Patent 2,334,864, issued Nov. 23, 1943; or the quaternary ammonium salts and polyethylene glycols of Piper U.S. Patent 2,886,437, issued May 12, 1959; and the polyethylene glycol type of Carroll and Beach U.S. Patent 2,708,162, issued May 10, 1955; or the thiopolymers of Graham and Sagal U.S. application Ser. No. 779,839, filed Dec. 12, 1958; or Dann and Chechak U.S. application Ser. No. 779,874, filed Dec. 12, 1958.

The sensitizers described above are advantageously incorporated in gelatin coatings contiguous to the evaporated silver halide layer. However, the sensitizers may be incorporated in any of the hydrophilic colloid binders referred to above which are useful as overcoatings to impart speed stability to elements of the type in which the light sensitive layer essentially consists of silver halide. The concentration of sensitizer, of course, depends upon the sensitizer and the particular silver halide layer to be sensitized, and varies over a wide range.

As used herein and in the appended claims, photographic sensitizers are used to,refer to all the chemical and spectral sensitizers which may be used in conventional photographic gelatin silver halide emulsions.

If desired, photographic elements of the invention may have vacuum deposited an alkali metal salt layer contiguous to the light sensitive silver halide layer as described in Rasch and Hodges U.S. patent application Ser. No. 361,243, filed Apr. 20, 1964, now abandoned.

Although hydrophilic overcoatings have previously been provided for conventional gelatin silver halide emulsions, the function of such overcoatings has been to provide protection, e.g., protection against abrasion, to the silver halide emulsion. Hydrophilic overcoatings for conventional silver halide emulsions do not function to stabilize the speed of the emulsion upon, storage. Hence, it was highly unexpected that the provision of a hydrophilic overcoating for light sensitive photographic elements of the type in which the light sensitive silver halide layer has been vacuum deposited, does function to stabilize the speed of such photographic elements.

Although the invention has been described in considerable detail with reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be effected without departing from the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A photographic element comprising a support having a light sensitive, vacuum deposited silver halide layer thereon, and a gelatin coating thereover to impart speed stability to the photographic element.

2. A photographic element comprising a support having a light-sensitive, vacuum-deposited silver halide layer thereon, and having a contiguous hydrophilic colloid layer containing a sensitizer for said silyer halide selected from the group consisting of water-soluble chemical sensitizers, water-soluble spectral sensitiziiig dyes and mixtures thereof.

3. A photographic element comprising a support having a light sensitive, vacuum deposited, silver halide layer thereon, and having coated thereover a gelatin layer containing a sensitizing amount of sodium aurous dithiosulfate and ammonium chloroiridite.

4. A photographic element comprising a support having a light sensitive, vacuum deposited silver halide layer thereon, and having coated thereover a gelatin layer containing a sensitizing amount of anhydro-9-methyl-3,3'- di(3-sulfobutyl)thiacarbocyaninehydroxide.

5. A photographic element comprising a support having a light sensitive, vacuum deposited silver halide layer thereon, and having coated thereover a gelatin layer containing a sensitizing amount of 3-car boxymethyl-5-[(3- ethyl-Z-benzothiazolinylidene)ethylidene] rhodanine.

6. A photographic element comprising a support having a light sensitive, vacuum deposited silver halide layer thereon, and having coated thereover a hydrophilic colloid layer containing a sensitizing amount of a dye selected from the group consisting of acid substituted cyanine dyes, acid substituted merocyanine dyes, and basic substituted merocyanine dyes.

7. The method of preparing a sensitized and speed stabilized photographic element which comprises vacuum depositing a light-sensitive silver halide layer on a support, and overcoating said layer with a hydrophilic colloid containing a sensitizer for said silver halide selected from the group consisting of water-soluble chemical sensitizers, water-soluble spectral sensitizing dyes and mixtures thereof.

References Cited UNITED STATES PATENTS 3,219,451 11/1965 LuValle et a1. 9694 3,368,895 2/1968 Matejec et a1. 96-94 3,219,450 11/ 1965 Goldberg 96-94 3,279,920 10/1966 Theodorou 9694 OTHER REFERENCES Goldberg et al.: Research on High Acuity Continuous Tone Vacuum Evaporated Silver Bromide Films, Technical Documentary Report No. ASDTDR63598, pp. 47-55, May 1963.

J. TRAVIS BROWN, Primary Examiner.

U.S. Cl. X.R. 

